Navy under fire side - Cause of stranding unclear

A necropsy report of a 2005 mass whale stranding on the North Carolina coast has identified no clear cause for the 36 whales to beach themselves, and no scientifically provable link to U.S. Navy ships and sonar activity in the area.

A necropsy report of a 2005 mass whale stranding on the North Carolina coast has identified no clear cause for the 36 whales to beach themselves, and no scientifically provable link to U.S. Navy ships and sonar activity in the area.

“Essentially we have been unable to provide a definitive reason for these strandings,” says Aleta Hohn, a NOAA marine mammal scientist.

Although there were lesions, or hemorrhaging, on different parts of most of the whales, their condition generally was good and the lesions weren’t consistent. Sonar has been linked to hemorrhaging around whales’ ears, brain, kidneys, lungs, oral cavities and blubber. The lesions the pathologists found could have been linked to other causes, such as beaching, parasites or diseases, she says.

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Thirty-three pilot whales stranded near Oregon Inlet and a single minke whale beached itself at Corolla, N.C., Jan. 14, 2005. The next day two dwarf sperm whales stranded north of Cape Hatteras. The pilots and dwarf sperm whales are warm-water species that likely would have been in the Gulf Stream, where Navy ships were using midfrequency sonar Jan. 12 to 14. Brandon Southall, NOAA’s acoustics program director, says the ships used their sonar sparingly during the exercises.

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Hohn says the Carolina coast’s gently sloping beach and sharp drop-off close to shore often are associated with mass strandings, as was the weather that day: heavy winds and powerful down- and upwelling currents. She says the strandings could have been caused by the combination of weather and oceanography. Also, four of the whales were diseased, and one could have beached itself, starting a stampede for shore.

“Whales are highly social animals and form cohesive groups,” she says. “They stay together.”

She says the incidents highlight that there’s a lot scientists don’t know about strandings — or their relationship to sonar.